Lens barrel and camera system

ABSTRACT

A lens barrel includes a fixed portion with an optical system including a focusing lens. An operation member is placed so as to be movable to first and second positions along an optical axis of the fixed portion, and turnable around the optical axis at the first and second positions. A turning member turns along with the operation member when moved to the second position, and does not operate with the operation member when moved from the second position to the first position. Positioning means position the operation member at the first or second position through a plurality of balls. When the operation member is at the first position it is urged to the first position by the plurality of balls. When the operation member is at the second position, it is urged to the second position by the plurality of balls.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/480,844, filed May 25, 2012, which claims the benefit of JapaneseApplication No. 2011-140803 filed in Japan on Jun. 24, 2011, thecontents of which are incorporated herein by this reference.

FIELD OF INVENTION

The present invention relates to a lens barrel which allows a movingposition of a focus lens to be specified by rotating an operation memberas well as to a camera system which uses the lens barrel. Moreparticularly, the present invention relates to a lens barrel whichallows a user to switch among plural manual focusing modes by moving theoperation member used to specify the moving position of the focus lensalong an optical axis as well as to a camera system which uses the lensbarrel.

BACKGROUND

A lens barrel is known which is equipped with a turnable operation ringon the lens barrel and is adapted to align distance informationindicated on the operation ring with aperture stop information indicatedon a fixed member when the operation ring is rotated, determine a movingposition of a focus lens, and move the focus lens to an absolutein-focus position using an actuator. Also, a lens barrel is known whichdisplays subject distance information in an information display windowduring manual focusing and hides the subject distance information duringautomatic focusing.

For example, a lens barrel disclosed in Japanese Patent ApplicationLaid-Open Publication No. 2011-33795 includes: a manual focus ring 43used to drive a lens barrel 6 to adjust focus when turned duringautomatic focusing or manual focusing; and a focus switching ring 47adapted to rotate around an optical axis and thereby move anintermediate ring 46 and a distance indicator ring 45 along the opticalaxis, where the intermediate ring 46 is connected to the focus switchingring 47 via a cam and the distance indicator ring 45 is turnably coupledto the intermediate ring 46, wherein during automatic focusing, thedistance indicator ring 45 and the manual focus ring 43 are decoupledfrom each other, making distance information no longer visible in aninformation display window of the focus switching ring 47, and duringmanual focusing, the distance indicator ring 45 and the manual focusring 43 are coupled to each other, making the distance informationvisible in the information display window of the focus switching ring47.

With the lens barrel disclosed in Japanese Patent Application Laid-OpenPublication No. 2011-33795 described above, switching between anautomatic focusing state and a manual focusing state is done by turningthe focus switching ring 47, and focus adjustment settings duringautomatic focusing or manual focusing can be made using a manual focusring 43 provided separately from the focus switching ring 47.

SUMMARY

The present invention provides a lens barrel comprising: a fixed portionin which an optical system including a focusing lens is placed; anoperation member placed so as to be movable to a first position and asecond position along an optical axis of the fixed portion and turnablearound the optical axis at each of the first position and the secondposition; a turning member adapted to turnably engage with the operationmember when the operation member moves to the second position, anddisengage from the operation member when the operation member moves fromthe second position to the first position; first detection means adaptedto detect a turning position of the turning member when the operationmember and the turning member turn in engagement at the second position;second detection means adapted to detect a turning amount and arotational direction of the operation member when the operation memberturns by being disengaged from the turning member after moving to thefirst position; and moving means placed in the fixed portion and adaptedto move the focusing lens along the optical axis based on acomputational value obtained by computation using at least an outputvalue from the first or second detection means.

Also, the present invention provides a camera system comprising a camerabody and a lens barrel detachable from the lens barrel, the camera bodyand the lens barrel being able to communicate with each other wherein:the lens barrel comprises: a fixed portion in which an optical systemincluding a focusing lens is placed, an operation member placed so as tobe movable to a first position and a second position along an opticalaxis of the fixed portion and turnable around the optical axis at eachof the first position and the second position, a turning member adaptedto turnably engage with the operation member when the operation membermoves to the second position, and disengage from the operation memberwhen the operation member moves from the second position to the firstposition, first detection means adapted to detect a turning position ofthe turning member when the operation member and the turning member turnin engagement at the second position, second detection means adapted todetect a turning amount and a rotational direction of the operationmember when the operation member turns by being disengaged from theturning member after moving to the first position, and moving meansplaced in the fixed portion and adapted to move the focusing lens alongthe optical axis; the camera body comprises control means adapted tomove the focusing lens along the optical axis by controlling the movingmeans based on an output from the first detection means or the seconddetection means; and the control means moves the focusing lens to apredetermined position starting from a current position of the focusinglens by an amount of travel based on the rotational direction andturning amount detected by the first detection means when moving thefocusing lens along the optical axis based on an output from the firstdetection means, and moves the focusing lens to a predeterminedcorresponding position using the turning position detected by the seconddetection means as an absolute position when moving the focusing lensalong the optical axis based on an output from the second detectionmeans.

Benefits of the invention will become more apparent from the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a camera system according to afirst embodiment of the present invention, with a lens barrel mounted ona camera body;

FIG. 2 is a block diagram of a configuration related to focusingoperation of the camera system of FIG. 1;

FIG. 3 is an overall view of the lens barrel with an operation ringlocated on a subject side position in the camera system of FIG. 1;

FIG. 4 is an overall view of the lens barrel with the operation ringlocated on a main body side position in the camera system of FIG. 1;

FIG. 5 is a sectional view of the lens barrel with the operation ringlocated on the subject side position in the camera system of FIG. 1;

FIG. 6 is a sectional view of the lens barrel showing a drive system ofa focus lens with the operation ring located on the subject sideposition in the camera system of FIG. 1;

FIG. 7 is a sectional view of the lens barrel with the operation ringlocated on the main body side position in the camera system of FIG. 1;

FIG. 8 is a perspective view illustrating a state in which the operationring and a distance indicator wheel are disengaged from each other inthe camera system of FIG. 1;

FIG. 9 is a perspective view illustrating a state in which the operationring and a distance indicator wheel are engaged with each other in thecamera system of FIG. 1;

FIG. 10 is a perspective view illustrating a configuration of an encoderunit in the camera system of FIG. 1;

FIG. 11 is a flowchart of a focusing operation mode determinationsubroutine for the camera system of FIG. 1;

FIG. 12 is a flowchart of automatic focusing operation in the camerasystem of FIG. 1;

FIG. 13 is a flowchart of manual focusing operation in the camera systemof FIG. 1;

FIG. 14 is a flowchart of distance-specified focusing operation in thecamera system of FIG. 1;

FIG. 15 is a perspective view showing a front side of a camera systemaccording to a second embodiment of the present invention;

FIG. 16 is a block diagram of a configuration related to focusingoperation of the camera system of FIG. 15;

FIG. 17 is a sectional view of a lens barrel with an operation ringlocated on the subject side position, according to a third embodiment ofthe present invention;

FIG. 18 is a sectional view of the lens barrel with the operation ringlocated on the main body side position in the camera system of FIG. 17;

FIG. 19 is a sectional view of a lens barrel with an operation ringlocated on the subject side position in a camera system according to afourth embodiment of the present invention;

FIG. 20 is a sectional view of the lens barrel with the operation ringlocated on the main body side position in the camera system of FIG. 19;and

FIG. 21 is a flowchart of a focusing operation mode determinationsubroutine for a camera system according to a fifth embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described belowwith reference to the accompanying drawings. In the drawings referred toin the following description, to make each component large enough to berecognized, scaling is varied from component to component, and thus itshould be noted that the present invention is not limited to quantities,shapes, size ratios, and relative positional relationships of thecomponents shown in the drawings.

First Embodiment

A camera system according to the present embodiment is an electroniccamera system which includes a camera body 2 and a lens barrel 10 asshown in FIG. 1. The electronic camera system is also referred to as adigital camera and configured to pick up and record subject imageselectronically.

In FIG. 1, the lens barrel 10 holds a photographic optical system 11made up of plural lenses including a focusing lens used to form subjectimages. The camera body 2 is provided with an image pickup device 9 (acharge-coupled device such as a CCD or a backside-illuminated CMOS(complimentary metal-oxide semiconductor) sensor) adapted to receive aphotographic light flux entering through the photographic optical system11, using a light-receiving surface (pixel area) and output anelectrical signal with a predetermined timing.

The camera body 2 and the lens barrel 10 are configured to be detachablefrom each other by means of an engaging mechanism generally known as abayonet mount. Incidentally, in the camera system 1, a mechanism whichallows the camera body 2 and the lens barrel 10 to be separable is notlimited to a mechanism according to the present embodiment. For example,a configuration generally know as a screw mount which uses a screwmechanism may be used or the camera body 2 and the lens barrel 10 may beconfigured to be separable by a mechanism which uses a fit or a magnet.

Furthermore, a release switch 3 and a power switch 4 are disposed on toppart of the camera body 2, where the release switch 3 is used by a userto enter an image pick up operation command and the power switch 4 isused by the user to enter a power ON/OFF operation command for thecamera body 2.

The release switch 3 is a pushbutton switch made up of two switches—afirst release switch 3 a and a second release switch 3 b—which areactivated depending on two different amounts of stroke (amounts ofdepression). Incidentally, the release switch 3 is not limited to aswitch in the form of a pushbutton, and may be another form of switchsuch as a touch sensor.

FIG. 2 illustrates a configuration of a system related to focusingoperation applied to the camera system 1 according to the presentembodiment.

As shown in FIG. 2, the release switch 3, the power switch 4, a focusingmode switching operation portion 5, a camera body control unit 6, animage processing unit 7, a communications unit 8, and the image pickupdevice 9 are disposed in the camera body 2, where the image pickupdevice 9 is an automatic focusing sensor unit.

The release switch 3 and the power switch 4 are as described above, andthus the other components will be described.

Although concrete configuration is not illustrated, the focusing modeswitching operation portion 5 shown in FIG. 2 is used to select anautomatic focusing operation mode for performing automatic focusingoperation or a manual focusing operation mode for performing manualfocusing operation. By operating the focusing mode switching operationportion 5, the user selects which modes to set, the normal automaticfocusing operation mode or the manual focusing operation mode.

Operation of the camera system 1 in the automatic focusing operationmode and the manual focusing operation mode will be described later.

Although concrete configuration is not illustrated, the focusing modeswitching operation portion 5 may be in the form of a button switch, atouch sensor, or a dial switch. For example, the camera body 2 may beequipped with an image display apparatus which displays a menu, allowingthe user to switch the focusing operation mode by selecting a menu itemvia a touch sensor or a button switch.

Alternatively, the focusing mode switching operation portion 5 may bedisposed on the lens barrel 10 rather than the camera body 2.

The camera body control unit 6 includes a computing unit (CPU), astorage device (RAM), input/output device, power control device, and thelike and controls operation of the camera body 2 based on apredetermined program.

The image processing unit 7 is an electronic circuit unit intended toperform image processing and adapted to form a subject image based on asignal outputted from the image pickup device 9 and calculate a contrastvalue during focusing based on the subject image.

A mounting pattern of the image processing unit 7 on the camera body 2may be in hardware form in which the image processing computationalhardware is mounted on the camera body 2 or in software form in whichthe computing unit of the camera body control unit 6 performs imageprocessing based on a predetermined image processing program.

The communications unit 8 is intended to conduct wired or wirelesscommunications with a lens barrel control unit 24 via a communicationsunit 25 provided in the lens barrel 10.

The image pickup device 9 described above is an automatic focusingsensor unit and is adopted to output a signal used to performcontrast-detection automatic focusing operation (autofocus operation).That is, after detecting the contrast value of the subject image basedon the signal outputted from the image pickup device 9 which is anautomatic focusing sensor unit, the camera system 1 according to thepresent embodiment performs focus adjustment of the photographic opticalsystem 11 in such a way as to maximize the contrast value.

Incidentally, the camera system 1 may be configured to perform automaticfocusing operation by means of so-called phase difference detection. Inthat case, in addition to the image pickup device 9, it is necessary todispose a sensor adapted to detect phase difference of the subject imageon the camera body 2. Also, the automatic focusing sensor unit may be asensor of another form such as a range sensor.

Next, a configuration related to focusing operation applied to the lensbarrel 10 will be described.

As shown in FIG. 2, an actuator 15, an operation ring turn detectionunit 21, an operation ring front/rear position detection unit 22, anencoder unit 23, the lens barrel control unit 24, and a communicationsunit 25 are disposed in the lens barrel 10.

The actuator 15 is a mechanism adapted to advanceably/retractably drivea focusing barrel 13 holding a focus lens 11 a of a photographic opticalsystem 11 (described later) along an optical axis. The actuator 15,whose details will be described later, is made up of a screw 15 a, astepping motor adapted to drive the screw 15 a, and others.

The operation ring turn detection unit 21 is detection means adapted todetect a turning direction and turning amount of an operation ring 17provided on the lens barrel 10, around an optical axis O. Also, theoperation ring front/rear position detection unit 22 is detection meansadapted to detect whether the operation ring 17 provided on the lensbarrel 10 is located on a subject side position (first position) or amain body side position (second position) along the optical axis O.

The encoder unit 23 is detection means adapted to detect a turningposition of a distance indicator wheel 18 when the operation ring 17provided on the lens barrel 10 is located at the main body side position(second position). Although details will be described later, the encoderunit 23 is designed to detect an absolute position around the opticalaxis O with respect to a base portion 12.

The lens barrel control unit 24 includes a computing unit, a storagedevice, an input/output device, and the like and controls operation ofthe lens barrel 10 based on a predetermined program. The communicationsunit 25 is intended to conduct wired or wireless communications with thecamera body control unit 6 via a communications unit 8 provided on thecamera body 2.

The above has been the configuration of the system related to focusingoperation applied to the camera system 1 according to the presentembodiment. Besides, although not illustrated, a battery housing unitadapted to house a primary battery or secondary battery intended tosupply power to the camera system 1 and a storage medium housing unitadapted to house a flash memory intended to store images are provided inthe camera body 2.

Next, a detailed configuration of the lens barrel 10 applied to thecamera system 1 according to the present embodiment will be describedwith reference to FIGS. 3 to 9.

FIGS. 3 and 4 are diagrams for illustrating an overall externalconfiguration of the lens barrel 10 and how a distance scale 18 aindicated on the distance indicator wheel 18 is concealed and revealedby the operation ring 17 when the operation ring 17 moves along theoptical axis O.

In FIG. 3, the base portion 12 is equipped with a bayonet unit 12 a foruse to detachably engage with an engaging portion (not shown) of thecamera body 2 and is fixed to the camera body 2 as the bayonet unit 12 aengages with the camera body 2. The base portion 12 makes up part of afixed member according to the present invention.

Being located in an outer circumferential portion of the lens barrel 10,the operation ring 17 is a substantially cylindrical member configuredto be able to be advanced and retracted by an operator between thesubject side position (first position) shown in FIG. 3 and the main bodyside position (second position) shown in FIG. 4 and disposed turnablyaround the optical axis O at each of the subject side position (firstposition) and the main body side position (second position). Theoperation ring 17 turns around the optical axis O under a force appliedto an operation portion 17 a by fingers of a user's hand. Also, as shownin FIGS. 3 and 4, the operation ring 17 is movable along the opticalaxis O within a predetermined range and is disposed so as to bepositioned selectively at one of both ends of the movable range when noexternal force is applied. That is, the operation ring 17 moves alongthe optical axis O from one end to the other end of the movable rangeunder the force applied to the operation portion 17 a by the user.

An index indicator barrel 16, which makes up part of a fixed memberaccording to the present invention in conjunction with the base portion12, has its position fixed with respect to the base portion 12 and makesup part of an exterior member of the lens barrel 10. The index indicatorbarrel 16 is provided with an index 16 a used to point at the distancescale 18 a provided on the distance indicator wheel 18 described later.Also, the index indicator barrel 16 has a depth-of-field index 16 bprovided on both sides of the index 16 a in a circumferential directionto indicate a depth of field index corresponding to an f-number of thephotographic optical system 11.

Incidentally, in FIG. 3, since the operation ring 17 is placed at thesubject side position (first position) by the operator, the distancescale 18 a provided on the distance indicator wheel 18 described lateris concealed by the operation ring 17.

FIG. 4 is a diagram showing a state which results when the operationring 17 is placed at the main body side position (second position) bythe operator. When the operation ring 17 is located on the main bodyside position (second position), the distance scale 18 a indicated onthe distance indicator wheel 18 is revealed.

Although details will be described later, the distance indicator wheel18 is turnable relative to the base portion 12. The distance indicatorwheel 18 is a turning member configured to engage with the operationring 17, becoming turnable around the optical axis O together with theoperation ring 17 when the operation ring 17 which is an operationmember is located on the main body side position (second position), anddisengage from the operation ring 17 when the operation ring 17 is movedto the subject side position (first position) shown in FIG. 3 from themain body side position (second position).

On the distance scale 18 a, numeric values which represent distancesranging from the closest focusing distance of the photographic opticalsystem 11 to infinity are arranged in the circumferential direction.When the distance indicator wheel 18 is turned relative to the indexindicator barrel 16 around the optical axis O, the numeric value on thedistance scale 18 a pointed at by the index 16 a changes.

For example, if the operator wants to shoot a subject located at adistance of approximately 1.2 m, the operator sets a manual focusingmode using the focusing mode switching operation portion 5 and thenplaces the operation ring 17 at the main body side position (secondposition). At the main body side position (second position), theoperator sets the index 16 a at approximately 1.2 m on the distancescale 18 a of the distance indicator wheel 18 by turning the operationring 17. Then, if an aperture of f/5.6 is used, it can be seen thatfocus is achieved in a range of 0.8 m to 3 m.

FIGS. 5 and 6 are sectional views taken along the optical axis O in FIG.3, showing a state which results when the operation ring 17 is placed atthe subject side position (first position) by the operator.

As shown in FIG. 5, the lens barrel 10 includes the base portion 12,focusing barrel 13, actuator 15, index indicator barrel 16, distanceindicator wheel 18, and operation ring 17 described above as well as thephotographic optical system 11 made up of fixed barrels 14, plurallenses, and the like, and a mechanism which holds the lenses.

The photographic optical system 11 includes the focus lens 11 a placedat the tail (image side) of the plural lenses and driven during focusingand a diaphragm mechanism 19 placed between a second group and a thirdgroup. The focus lens 11 a, which is held by the focusing barrel 13disposed advanceably/retractably relative to the base portion 12 alongthe optical axis O, is moved relatively along the optical axis O by theactuator 15 based on a detection signal (described later) and therebydriven to an in-focus position.

Incidentally, the photographic optical system 11 may be a folded opticalsystem which includes a prism, mirror, and the like in addition tolenses. Also, a filter and the like may be included in the photographicoptical system 11.

A first fixed barrel 14 a and second fixed barrel 14 b both annular inshape are fixed to the base portion 12. The annular first fixed barrel14 a and the annular second fixed barrel 14 b correspond to a fixedportion according to the present invention or part of the fixed portion.The first fixed barrel 14 a is fixed to the base portion 12 with pluralscrews 14 f while the second fixed barrel 14 b is fixed to the firstfixed barrel 14 a with plural screws 14 g.

Plural through-holes 14 c are formed circumferentially in the firstfixed barrel 14 a in order for balls 14 d to fit in loosely.

The through-holes 14 c are provided in locations where the balls 14 drest against a rib portion 17 c of the operation portion 17 a placed onan outer circumferential portion of the first fixed barrel 14 a. Theballs 14 d loosely fitted in the through-holes 14 c can protrude outwardfrom an outer circumferential surface of the first fixed barrel 14 a,being urged radially outward by an urging member 14 e which is a leafspring.

The rib portion 17 c includes a first sloping portion 17 d configured toprotrude radially inward, shaped substantially triangular in crosssection, and formed circumferentially around the entire circumference;and a second sloping portion 17 e formed on a front side of the firstsloping portion 17 d. An inside diameter of the first sloping portion 17d decreases forward along the optical axis O while an inside diameter ofthe second sloping portion 17 e increases forward along the optical axisO.

When the operation portion 17 a is placed at the subject side position(first position), the balls 14 d are urged by the urging member 14 etoward the first sloping portion 17 d of the rib portion 17 c of theoperation portion 17 a, maintaining the position of the operationportion 17 a.

Incidentally, the balls 14 d abut the first sloping portion 17 d of therib portion 17 c when the operation portion 17 a is located at thesubject side position (first position) (see FIG. 5), and abut the secondsloping portion 17 e of the rib portion 17 c when the operation portion17 a is at the main body side position (second position) (see FIG. 7).Since the rib portion 17 c has a substantially triangular crosssectional shape, the balls 14 d always abut either the first slopingportion 17 d or the second sloping portion 17 e regardless of theposition of the operation portion 17 a.

Therefore, when located at the subject side position (first position),the operation portion 17 a is urged forward by the balls 14 d placed inabutment with the first sloping portion 17 d and positioned against oneend of the movable range at the first position.

On the other hand, as disclosed in FIG. 7, when located at the main bodyside position (second position), the operation portion 17 a is urgedtoward the main body side by the balls 14 d placed in abutment with thesecond sloping portion 17 e and positioned against the other end of themovable range at the second position.

The operation ring 17 is made up of the operation portion 17 a and aninner cylindrical portion 17 b which are formed into an integral unit,where the operation portion 17 a is configured to be substantiallytubular in shape, exposed from an outer circumferential surface of thelens barrel 10, and provided with a straightly-knurled outercircumferential portion to be held by fingers of a user's hand while theinner cylindrical portion 17 b is disposed inside the operation portion17 a with a predetermined clearance. According to the present embodimentillustrated in FIGS. 3 to 9, the operation portion 17 a and the innercylindrical portion 17 b are different members which are fastenedtogether, for example, by an adhesive or screws to make up the operationring 17, but the operation portion 17 a and the inner cylindricalportion 17 b may be made of the same member as an integral member.

The inner cylindrical portion 17 b is provided with an engaging portion17 g intended to integrally rotate the operation ring 17 and thedistance indicator wheel 18 by engaging with the distance indicatorwheel 18 when the operation ring 17 is located at the main body sideposition (second position).

Also, an engaging pin 18 b is provided on an inner circumferentialportion of the distance indicator wheel 18, protruding radially inward.According to the present embodiment, the engaging pin 18 b is made of amember different from a member of the distance indicator wheel 18 andfastened to the distance indicator wheel 18 by press-fitting or anadhesive. However, the engaging pin 18 b may be formed integrally withthe distance indicator wheel 18.

Incidentally, a relationship of engagement between the inner cylindricalportion 17 b and the engaging pin 18 b provided on the innercircumferential portion of the distance indicator wheel 18 will bedescribed later.

Also, the operation ring turn detection unit 21 is disposed on thesecond fixed barrel 14 b of the lens barrel 10 to detect the turningdirection and turning amount of the inner cylindrical portion 17 b ofthe operation ring 17 around the optical axis O when the operation ring17 is located on the subject side (first position). The operation ringturn detection unit 21 is disposed on the subject side of the secondfixed barrel 14 b. Also, since the inner cylindrical portion 17 b is acomponent of the operation ring 17, the turning direction and turningamount of the operation ring 17 can be detected by detecting theposition of the inner cylindrical portion 17 b.

Furthermore, the operation ring front/rear position detection unit 22 isdisposed on the first fixed barrel 14 a of the lens barrel 10 to detectwhether the operation ring 17 is located at the first position or thesecond position along the optical axis O. The operation ring front/rearposition detection unit 22 is placed in a main-body-side end portion ofthe first fixed barrel 14 a.

FIG. 6 is a sectional view taken along the optical axis O in FIG. 3, butis different from the sectional view of FIG. 5. Also, FIG. 6 is adiagram for illustrating a configuration of the actuator 15 adapted todrive the focus lens 11 a. The same components as those in FIG. 5 aredenoted by the same reference numerals as the corresponding components.

In FIG. 6, the actuator 15 adapted to drive the focus lens 11 a isplaced in an inner circumferential portion of the first fixed barrel 14a. The configuration of the actuator 15 is not particularly limited.However, according to the present embodiment, the actuator 15 includesthe screw 15 a disposed substantially parallel to the optical axis O, astepping motor 15 c adapted to rotate the screw 15 a, and a nut 15 badapted to screw onto the screw 15 a. The nut 15 b which makes up partof the actuator 15 is engaged with the focusing barrel 13 configured tohold the focus lens 11 a and follow the nut 15 b.

The actuator 15 controls the stepping motor 15 c based on computationalvalues resulting from computations performed by the lens barrel controlunit 24 based on output from the operation ring turn detection unit 21or the encoder unit 23 described with reference to FIG. 2. The steppingmotor 15 c drives the nut 15 b along the optical axis O by rotating thescrew 15 a. The focusing barrel 13 with the focus lens 11 a providedthereon is driven along the optical axis O by a predetermined amount byfollowing the nut 15 b.

Incidentally, the configuration of the actuator 15 is not limited tothat of the present embodiment, and another type such as a linear motormay be used alternatively. Also, the actuator 15 may be configured suchthat some components such as the stepping motor will be disposed in thecamera body 2.

FIG. 7 is a sectional view taken along the optical axis O in FIG. 4,showing a state which results when the operation ring 17 is placed atthe main body side position (second position) by the operator.

As described above, when the operation ring 17 is moved to the main bodyside position (second position) by the operator, the balls 14 d abut thesecond sloping portion 17 e of the rib portion 17 c provided on an innercircumferential portion of the operation portion 17 a, causing theoperation portion 17 a to be held at the main body side position (secondposition).

Also, since the operation ring 17 is placed at the main body sideposition (second position) by the operator, the distance scale 18 a ofthe distance indicator wheel 18 is revealed as shown in FIG. 4.Furthermore, since the engaging portion 17 g of the inner cylindricalportion 17 b provided integrally with the operation portion 17 a engageswith the pin 18 b of the distance indicator wheel 18, the distanceindicator wheel 18 is turnable along with the operation portion 17 a.

FIGS. 8 and 9 are diagrams for illustrating a relationship of engagementbetween the operation ring 17 and the distance indicator wheel 18 aswell as position detection of the operation ring 17, where the operationring 17 is made up of the operation portion 17 a and the innercylindrical portion 17 b: FIG. 8 is a diagram for illustrating a statewhich results when the operation portion 17 a is moved to the subjectside (first position) while FIG. 9 is a diagram for illustrating a statewhich results when the operation portion 17 a is moved to the main bodyside position (second position).

As shown in FIG. 8, plural slit holes 17 f are provided at equalintervals in the circumferential direction in one subject-side endportion of the inner cylindrical portion 17 b of the operation ring 17.

As described with reference to FIGS. 5 and 7, the operation ring turndetection unit 21 is provided on the second fixed barrel 14 b of thelens barrel 10. The operation ring turn detection unit 21 is a pair ofphotointerrupters which detect passage of the plural slit holes 17 fprovided in the inner cylindrical portion 17 b of the operation ring 17,and then detect the turning direction and turning amount of theoperation ring 17 based on a resulting output signal. The operation ringturn detection unit 21 according to the present embodiment and the slitholes 17 f provided in the operation ring 17 have a form similar to thatof a so-called incremental rotary encoder.

Only when the operation ring 17 is located at the subject side position(first position), the pair of photointerrupters detect the subject-sideend portion of the inner cylindrical portion 17 b where the slit holes17 f are formed. Therefore, the turning direction and turning amount ofthe operation ring 17 around the optical axis O can be detected onlywhen the operation ring 17 is located at the first position, i.e., whenthe pair of photointerrupters are within a detection range.

The form of the operation ring turn detection unit 21 is not limited tothat of the present embodiment as long as the turning direction andturning amount of the operation ring 17 around the optical axis O can bedetected at least when the operation ring 17 is located at the subjectside position (first position). For example, the operation ring turndetection unit 21 may be in the form of a magnetic rotary encoder.

Also, on an outer circumferential surface of the inner cylindricalportion 17 b, plural projections of the engaging portion 17 g arearranged in the circumferential direction, protruding radially outwardand being spaced at predetermined intervals. When the plural projectionsare viewed radially from the outside, rear part of the pluralprojections are substantially V-shaped (on the main body side),narrowing in width toward the main body side.

As can be seen from FIGS. 5 and 8, the distance indicator wheel 18 isdisposed between the operation portion 17 a and inner cylindricalportion 17 b of the operation ring 17. The engaging pin 18 b disposedinside the distance indicator wheel 18 protrudes toward the outercircumferential surface of the inner cylindrical portion 17 b. As shownin FIG. 8, the engaging pin 18 b is disposed singly in a main-body-sideend portion of the distance indicator wheel 18. An inside diameter ofthe engaging pin 18 b is smaller than an outside diameter of theengaging portion 17 g made up of the plural projections protrudingradially outward.

Also, the engaging pin 18 b is shaped so as to fit, with a predeterminedclearance, in any of spaces between the projections arranged in thecircumferential direction of the engaging portion 17 g.

As shown in FIG. 5, when the operation ring 17 is located on the subjectside (first position), the engaging pin 18 b is located c loser to themain body side than is the engaging portion 17 g of the operation ring17 and is disposed in such a position as neither engage with, of course,nor interface with the engaging portion 17 g even if the operation ring17 is turned around the optical axis O. Therefore, when the operationring 17 is located at the subject side position (first position), theengaging pin 18 b remains stopped without turning even if the operationring 17 is turned around the optical axis O.

Also, as shown in FIGS. 7 and 9, when the operation ring 17 is at themain body side position (second position), the engaging pin 18 b isdisposed at such a position as to overlap the engaging portion 17 g in adirection perpendicular to the direction of the optical axis O. That is,when the operation ring 17 is at the main body side position (secondposition), the engaging pin 18 b fits in any of spaces between theprojections arranged in the circumferential direction of the engagingportion 17 g, allowing the operation ring 17 and the distance indicatorwheel 18 to turn together around the optical axis O.

As described above, since the plural projections of the engaging portion17 g are substantially V-shaped on the main body side as viewed radiallyfrom the outside, when the operation ring 17 is moved from the subjectside position (first position) to the main body side position (secondposition), the substantially V-shaped portion follows the engaging pin18 b, turning the distance indicator wheel 18 slightly and therebycausing the engaging pin 18 b and the engaging portion 17 g to engagewith each other smoothly. Consequently, the operation ring 17 movesalong the optical axis O without a hitch, and thus can be moved quickly.

A turning range of the distance indicator wheel 18 is limited to a rangein which a combination of the distance scale 18 a and index 16 aindicates numeric values of distances from the closest focusing distanceof the photographic optical system 11 to infinity. Therefore, whenengaged with the distance indicator wheel 18 at the main body sideposition (second position), the operation ring 17 is set to turn only atpredetermined angles within the same turning range as the distanceindicator wheel 18. On the other hand, when the operation ring 17 is atthe subject side position (first position), since the operation ring 17does not interfere with the distance indicator wheel 18, there is nolimit to the turning range of the operation ring 17.

As shown in FIGS. 5, 7, and 9, the operation ring front/rear positiondetection unit 22 is a photointerrupter adapted to detect whether theoperation ring 17 is located on the subject side (first position) or themain body side (second position). The operation ring front/rear positiondetection unit 22 is fixed to the base portion 12 which makes up thefixed portion according to the present invention or the fixed barrels 14which make up the fixed portion according to the present invention.According to the present embodiment, the operation ring front/rearposition detection unit 22 is fixed to the base portion 12 and adaptedto detect that a part of the operation ring 17 has advanced to the mainbody side (second position).

Incidentally, the form of the operation ring front/rear positiondetection unit 22 is not particularly limited as long as the position ofthe operation ring 17 along the optical axis O can be detected. Forexample, the operation ring front/rear position detection unit 22 may bea magnetic sensor or the like.

FIG. 10 is a diagram for illustrating detection means adapted to detectabsolute position of the distance indicator wheel 18 which turnstogether with the operation ring 17 on the main body side (secondposition) when the operation ring 17 is detected to be located on themain body side (second position).

As shown in FIGS. 2 and 10, the encoder unit 23 adapted to detect anabsolute turning position of the distance indicator wheel 18 around theoptical axis O with respect to the base portion 12 is disposed in thelens barrel 10 according to the present embodiment. The encoder unit 23is configured in the form of a so-called absolute rotary encoder. Theencoder unit 23 includes a code pattern 23 a of a predetermined bitcount and a contact portion 23 b adapted to slide over the code pattern23 a, where both the code pattern 23 a and contact portion 23 b are madeof a conductive material.

The code pattern 23 a is disposed in an outer circumferential portion ofthe distance indicator wheel 18 and the contact portion 23 b is disposedon the second fixed barrel 14 b. A contact position of the contactportion 23 b on the code pattern 23 a changes with the turning positionof the distance indicator wheel 18 around the optical axis O. Althoughnot illustrated, the encoder unit 23 includes an electric circuitadapted to detect a state of contact between the code pattern 23 a andthe contact portion 23 b, and the absolute turning position of thedistance indicator wheel 18 around the optical axis O with respect tothe base portion 12 can be calculated based on a result of thedetection.

The absolute turning position here is the position of the focus lens 11a and is determined in advance based on the state of contact between thecode pattern 23 a and the contact portion 23 b. Based on output from thelens barrel control unit 24 and according to the state of contact, theactuator 15 described above drives the focus lens 11 a to the positiondetermined in advance (absolute position).

Incidentally, the configuration of the encoder unit 23 is not limited tothat of the present embodiment as long as the absolute turning positionaround the optical axis O with respect to the base portion 12 can bedetected. For example, the encoder unit 23 may be an optical ormagnetic, absolute rotary encoder or may have a configuration similar tothat of a so-called potentiometer whose resistance changes with theturning position of the distance indicator wheel 18 around the opticalaxis O.

Also, other lenses of the photographic optical system 11 may be drivenby the actuator 15 in addition to the focus lens 11 a.

Next, operation of the camera system 1 according to the presentembodiment will be described.

With the camera system 1 according to the present embodiment, when poweris turned on and the camera body is in photo mode, the camera bodycontrol unit 6 runs a focusing operation mode determination subroutineshown in FIG. 11 in predetermined cycles. The focusing operation modedetermination subroutine causes the focusing mode switching operationportion 5 to determine a focusing operation mode selected from amongplural focusing operation modes of the camera system 1 based on a usercommand entered by a user and switches operation mode of the camerasystem 1 according to the user command.

In FIG. 11, according to the focusing operation mode determinationsubroutine, first in step S01, the camera system 1 determines whetherthe mode selected by the user using the focusing mode switchingoperation portion 5 is manual focusing operation mode or automaticfocusing operation mode. If it is determined in step S01 that theautomatic focusing operation mode is selected, the camera system 1 goesto step S03 to switch the operation of the camera system 1 to automaticfocusing operation. Once step S03 is executed, the camera system 1performs the automatic focusing operation shown in FIG. 12.

On the other hand, if it is determined in step S01 that the automaticfocusing operation mode is not selected, i.e., if the camera system 1 isin the manual focusing operation mode in which the contrast-detectionautomatic focusing operation (autofocus operation) based on a signalfrom the image pickup device 9 is not performed, the camera system 1goes to step S02 to determine whether the operation ring 17 exists onthe subject side (first position) or the main body side (secondposition) based on an output signal from the operation ring front/rearposition detection unit 22. If it is determined in step S02 that theoperation ring 17 exists at the subject side (first position) position,the camera system 1 goes to step S04 to switch the operation of thecamera system 1 so as to perform manual focusing operation.

Once step S04 is executed, the camera system 1 performs the manualfocusing operation shown in FIG. 13. Although concrete operation will bedescribed with reference to FIG. 13, the manual focusing operation,which is performed when a turn of the operation ring 17 is detected bythe operation ring turn detection unit 21, involves driving the focusingbarrel 13 according to the turning direction and turning amount of theoperation ring 17 turned manually.

On the other hand, if it is determined in step S02 that the operationring 17 does not exist on the subject side (first position), i.e., if itis determined that the operation ring 17 exists on the main body side(second position), the camera system 1 goes to step S05 to switch theoperation of the camera system 1 so as to perform distance-specifiedfocusing operation.

Although concrete operation will be described with reference to FIG. 14,the distance-specified focusing operation, which is performed when it isdetermined that the operation ring 17 exists on the main body side(second position), involves detecting the position of the operation ring17 turned manually, as an absolute position, using the encoder unit 23and driving the focusing barrel 13 (focus lens 11 a) to the position(absolute position) determined in advance based on the state of contactbetween the code pattern 23 a and the contact portion 23 b.

In steps S03 to S05, the camera system 1 is switched to respectiveoperations, and corresponding subroutines shown in FIGS. 12 to 14 areexecuted. After any of the subroutines is executed, the camera system 1returns to a main sequence of the camera.

A flowchart in FIG. 12 is an automatic focusing operation subroutine towhich the camera system 1 is switched in step S03. If the first releaseswitch 3 a is activated by a half-press in step S10, automatic focusingoperation is performed. In step S11, the camera system 1 detects acontrast value of the subject based on a signal outputted from the imagepickup device 9 serving as the automatic focusing sensor unit and drivesthe focusing barrel 13 in such a way as to maximize the contrast value.Once the subroutine ends, the camera system 1 returns to the mainsequence of the camera.

For example, in the case of the camera system 1 in which the camera body2 and the lens barrel 10 are configured to be separable as with thepresent embodiment, to perform automatic focusing operation, the camerabody control unit 6 issues instructions to drive the focusing barrel 13.In this case, to perform focus adjustment based on a signal outputtedfrom the image pickup device 9, the lens barrel control unit 24 of thelens barrel 10 drives the focusing barrel 13 according to theinstructions issued by the camera body control unit 6 and inputted viathe communications unit 25.

In the case of the camera system 1 according to the present embodiment,automatic focusing operation is performed when the automatic focusingoperation mode is selected and the operation ring 17 is at the subjectside (first position) position. This is to give priority to the distanceindicated by the distance scale 18 a and index 16 a, for example, whenthe distance is set to 1 m with the operation ring 17 placed on the mainbody side (second position) where the distance scale 18 a is exposed tothe outside, and thereby prevent focusing at infinity rather than at thedistance of 1 m.

Incidentally, to deal with a situation in which a main subject movesfast, settings may be made to allow automatic focusing operation to beperformed even after the operation ring 17 is moved to the main bodyside (second position). This will make it possible to achieve focusquickly, for example, even if the main subject moves quickly to adistance of 3 m after the distance is set to 1 m.

A flowchart in FIG. 13 is a manual focusing operation subroutine towhich the camera system 1 is switched in step S04.

In step S20, the camera system 1 determines whether or not a turn of theoperation ring 17 existing at the subject side (first position) positionhas been detected. If a turn of the operation ring 17 has been detected,the camera system 1 goes to step S21. In step S21, the camera system 1makes the operation ring turn detection unit 21 detect the turningdirection (turning angular velocity) and turning amount (turning angle)of the operation ring 17 turned manually at the subject side (firstposition) position. Then, based on results thus produced, the lensbarrel control unit 24 drives the focusing barrel 13 by controlling theactuator 15. Once the subroutine shown in FIG. 13 ends, the camerasystem 1 returns to the main sequence of the camera.

On the other hand, if no turn of the operation ring 17 existing at thesubject side (first position) position is detected in step S20, thecamera system 1 maintains the state of manual focusing operation untilthe automatic focusing operation mode is selected via the focusing modeswitching operation portion 5 provided on the camera body or theoperation ring 17 provided on the lens barrel is moved from the subjectside position (first position) to the main body side position (secondposition).

A flowchart in FIG. 14 is a distance-specified focusing operationsubroutine to which the camera system 1 is switched in step S05.

In step S30, if it is detected that the operation ring 17 is located atthe main body side position (second position) and the operation ring 17is turned as well, the lens barrel control unit 24 reads an output valueof the encoder unit 23 and detects the turn of the operation ring 17.The output value of the encoder unit 23 represents the absolute turningposition of the distance indicator wheel 18 around the optical axis Owith respect to the base portion 12. Once the turn of the operation ring17, i.e., the output value of the encoder unit 23 is read by the encoderunit 23, the camera system 1 goes to step S31.

Next, in step S31, based on a conversion table prestored in a memory(not shown), the lens barrel control unit 24 calculates the numericvalue of distance indicated by the distance scale 18 a and index 16 afrom the output value of the encoder unit 23.

After the numeric value of distance indicated by the distance scale 18 aand the index 16 a is calculated by the lens barrel control unit 24, instep S32, the camera system 1 moves the focusing barrel 13 by drivingthe actuator 15 such that the focusing distance of the photographicoptical system 11 will match the numeric value calculated by the lensbarrel control unit 24. For example, if the numeric value of distanceindicated by the distance scale 18 a and the index 16 a is 3 m, thefocusing barrel 13 is moved such that the focusing distance of thephotographic optical system 11 will be 3 m. Once the subroutine shown inFIG. 14 ends, the camera system 1 returns to the main sequence of thecamera.

Ideally the focusing distance of the photographic optical system 11coincides with the numeric value of distance indicated by the distancescale 18 a and the index 16 a, but if the encoder unit 23 has a lowresolution, it is difficult to bring the two values into coincidence,and thus the focusing barrel 13 may be moved such that the two valueswill be approximately equal.

When the focusing barrel 13 is moved by distance-specified focusingoperation subroutine, the lens barrel control unit 24 outputs thecalculated numeric value of the distance indicated by the distance scale18 a and the index 16 a to the camera body control unit 6 of the camerabody 2 via the communications unit 25. The camera body control unit 6determines an exposure value according to the received numeric value andattaches the numeric value as metadata to a photographed image.

The distance-specified focusing operation is maintained until theautomatic focusing operation mode is selected via the focusing modeswitching operation portion 5 provided on the camera body or theoperation ring 17 provided on the lens barrel is moved from the mainbody side position (second position) to the subject side position (firstposition).

With any of the manual focusing operation and distance-specifiedfocusing operation subroutines, the lens barrel control unit 24 movesthe focusing barrel 13 in such a direction as to reduce the focusingdistance of the photographic optical system 11 when a clockwise turn ofthe operation ring 17 is detected as the lens barrel 10 is viewed fromthe main body side, and moves the focusing barrel 13 in such a directionas to increase the focusing distance of the photographic optical system11 when a counterclockwise turn of the operation ring 17 is detected.

As described above, the camera system 1 according to the presentembodiment allows the user to select one of the automatic focusingoperation and manual focusing operation by operating the focusing modeswitching operation portion 5 or the operation ring 17.

When the automatic focusing operation is selected and the operation ring17 is located at the subject side position (first position), focusadjustment is performed based on output from the image pickup device 9serving as the focusing sensor unit regardless of the turning positionof the distance indicator wheel 18. When the manual focusing operationis selected, the manual focusing operation described above can beselected by moving the operation ring 17 to the main body side position(second position) or the subject side position (first position).

More specifically, when the manual focusing operation mode is selectedvia the focusing mode switching operation portion 5 and the operationring 17 is located on the subject side (first position), focusadjustment can be performed based on current position of the focus lens11 a by turning the operation ring 17. In the above-described manualfocusing operation, since the operation ring 17 and the distanceindicator wheel 18 are not engaged with each other, the operation ring17 can be turned around the optical axis O without limit, and the focusadjustment of the focus lens 11 a of the photographic optical system 11is performed according to the turning amount of the operation ring 17based on the current position of the focus lens 11 a.

Such manipulations enable finer focus adjustment than thedistance-specified focusing operation by means of a distance scale andare useful in macro photography or in photographic conditions underwhich the user wants to make a finer focus adjustment, moving furtherfrom a current focus adjustment state.

Also, when the manual focusing operation mode is selected via thefocusing mode switching operation portion 5 and the operation ring 17 islocated at the main body side position (second position), manualfocusing can be performed using the distance scale. That is, by visuallyconfirming the distance scale 18 a, the index 16 a, and thedepth-of-field index 16 b exposed on the outer circumferential portionof the lens barrel 10, the user can promptly verify and set the subjectdistance to be focused at.

Once the subject distance is set promptly during the distance-specifiedfocusing operation, the focusing barrel 13 is forcibly driven to theposition corresponding to the numeric value of distance indicated by thedistance scale 18 a and index 16 a and calculated from an output signalof the encoder unit 23. Therefore, when the user wants to quickly set toa distance confirmed visually or a distance known in advance, bymanually setting the distance scale 18 a to a predetermined focusingdistance, the user can carry out a photographic technique forphotographing quickly without performing focus adjustment operation.

Thus, the camera system 1 according to the present embodiment makes itpossible to selectively perform the distance-specified focusingoperation and the manual focusing operation by moving the operation ring17 forward or backward once, where the distance-specified focusingoperation enables quick photographing by clearly showing a focusingdistance and depth of field although focus adjustment is coarse and themanual focusing operation enables fine focus adjustment.

Since switching between the distance-specified focusing operation andthe manual focusing operation can be done by simply moving the operationring 17 forward or backward, the present embodiment can also be used toset to the desired focusing distance by manual focusing the distancescale and make a finer focus adjustment, moving further from the currentfocus adjustment state if the operation ring 17 is moved to the mainbody side position (second position), the operation ring 17 is turned,the distance scale 18 a is manually set to a predetermined desiredfocusing distance, and then the operation ring 17 is moved to thesubject side (first position). This makes it possible to more quicklyperform focus adjustment as desired.

This is because the present embodiment is configured such that when theoperation ring 17 is located at the subject side position (firstposition), the operation ring 17 and the distance indicator wheel 18will not be engaged with each other, disabling the distance indicatorwheel 18 from turning even if the operation ring 17 turns. Moreover, thefocusing distance established during the distance-specified focusingoperation in which the operation ring 17 is located at the main bodyside position (second position) is not changed unless the manualfocusing operation mode is set by moving the operation ring 17 to thesubject side position (first position).

Also, the present embodiment can be used in the following manner.

In distance-specified focusing operation, the user can, for example,place the operation ring 17 at the main body side position (secondposition), preset the focusing distance to 3 meters by rotating thedistance indicator wheel 18, subsequently move the operation ring 17 tothe subject side position (first position), and adjust focus by manualfocusing operation. Even if focus is adjusted by manual focusingoperation, since the distance indicator wheel 18 does not turn, if theuser subsequently wants to take a photograph, for example, at a focusingdistance of 2 meters, the user can promptly set the focusing distance ofthe photographic optical system 11 to 2 meters by moving the operationring 17 to the main body side position (second position).

In this way, if the focusing distance is set in advance to a desiredvalue during distance-specified focusing operation, the user can take aphotograph quickly at a desired focusing distance by simply moving theoperation ring 17 backward from a state of performing manual focusingoperation.

In the lens barrel 10 of the camera system 1 according to the presentembodiment, since the actuator 15 drives only the focusing barrel 13which holds the focusing photographic optical system 11 a, the memberdriven by the actuator 15 can be made lightweight. Consequently,according to the present embodiment, the actuator 15 can be small inoutput and size, making it possible to downsize the lens barrel 10.

Furthermore, the present embodiment eliminates the need for a mechanismfor transmitting power used to drive the distance indicator wheel 18,making it possible to transmit power from the actuator 15 to thefocusing barrel 13 which is a driven member using a simple configurationwith a small number of parts. This makes it easy to reduce volume ofsound produced when the focusing barrel 13 is driven for focusadjustment. In particular, in shooting of moving images, the reductionof sound produced during focus adjustment has a great effect.

Incidentally, the lens barrel 10 according to the present embodiment hasthe form of a so-called single-focus lens which has fixed focal length,and the lenses other than the focus lens 11 a of the photographicoptical system 11 are held by the fixed barrels 14. However, if the lensbarrel 10 is a so-called collapsible lens barrel whose overall length isexpandable/collapsible, or a zoom lens or varifocal lens whose focallength is variable, plural barrel members may be used to hold the lensesother than the focus lens 11 a and moved relative to the base portion12.

As described so far, the present embodiment provides a lens barrel andcamera system which allow the user, upon entering manual focusing mode,to switch to the distance-specified focusing operation mode that usesthe distance scale or to the manual focusing operation mode with asingle operation according to a photography scene and perform focusadjustment in the selected mode.

Also, after the switching, the lens barrel and camera system allow theuser to check focusing state quickly based on the position of theoperation ring 17. Furthermore, being capable of reducing the output andsize of the actuator 15, the lens barrel and camera system make itpossible to downsize the camera and the camera system.

Second Embodiment

A second embodiment of the present invention will be described belowwith reference to FIGS. 15 and 16.

Differences from the first embodiment will only be described below,wherein components similar to those of the first embodiment are denotedby the same reference numerals as the corresponding components, anddescription thereof will be omitted as appropriate.

As shown in FIG. 15, the camera system 1 according to the presentembodiment is configured to be an integral unit such that the camerabody 2 and the lens barrel 10 will be inseparable. In the camera system1 in which the camera body 2 and the lens barrel 10 are formedintegrally as with the present embodiment, there is no need to dispose aseparate control unit in both the camera body 2 and lens barrel 10, anda single control unit will suffice.

FIG. 16 is a diagram showing the lens barrel 10 according to the firstembodiment with the lens barrel control unit 24 and the communicationsunit 25 omitted, wherein the only control unit is the camera bodycontrol unit 6 disposed in the camera body 2. The camera body controlunit 6 is configured to be able to also perform the control performed bythe lens barrel control unit in the first embodiment. Regarding the restof the configuration and operation, the camera system 1 according to thepresent embodiment is similar to the first embodiment. Thus, the camerasystem 1 according to the present embodiment provides advantages similarto those of the first embodiment.

Third Embodiment

A third embodiment of the present invention will be described below withreference to FIGS. 17 and 18.

The third embodiment differs from the first embodiment only in how theoperation ring 17 and the distance indicator wheel 18 are configured tobe engaged with each other. Differences from the first embodiment willonly be described below, wherein components similar to those of thefirst embodiment are denoted by the same reference numerals as thecorresponding components, and description thereof will be omitted asappropriate.

FIG. 17 is a sectional view of the lens barrel 10 in a state in whichthe operation ring 17 is located on the subject side (first position)and the operation ring 17 and the distance indicator wheel 18 are notengaged. FIG. 18 is a sectional view of the lens barrel 10 in a state inwhich the operation ring 17 is located on the body side (secondposition) and the operation ring 17 and the distance indicator wheel 18are engaged.

A feature of the present embodiment is that the operation ring 17 andthe distance indicator wheel 18 are engaged with each other by frictiontherebetween.

In FIGS. 17 and 18, a flange portion 17 h is provided on the outercircumferential portion of the inner cylindrical portion 17 b of theoperation ring 17, protruding radially outward. On the other hand, aflange portion 18 c is provided on the distance indicator wheel 18disposed on the outer circumference of the inner cylindrical portion 17b, protruding radially inward at a location closer to the main body sidethan is the flange portion 17 h.

As shown in FIG. 17, when the operation ring 17 is located at the firstposition, the flange portion 17 h of the inner cylindrical portion 17 band the flange portion 18 c of the distance indicator wheel 18 face eachother, being spaced away from each other along the optical axis O, andno frictional force acts between the flange portion 17 h and the flangeportion 18 c. Consequently, the distance indicator wheel 18 does notturn even if the operation ring 17 turns.

On the other hand, as shown in FIG. 18, when the operation ring 17 islocated at the second position, since the operation ring 17 is urgedbackward relative to the distance indicator wheel 18 by the urgingmember 14 e and the balls 14 d, the inner cylindrical portion 17 b ofthe operation ring 17 is pressed against the flange portion 18 c of thedistance indicator wheel 18 along the optical axis O by the urgingforce, coming into abutment with the latter. Contact surfaces betweenthe inner cylindrical portion 17 b of the operation ring 17 and theflange portion 18 c of the distance indicator wheel 18 are structured toproduce frictional forces against each other, causing the operation ring17 and the distance indicator wheel 18 to turn together.

Specifically, the inner cylindrical portion 17 b of the operation ring17 and the flange portion 18 c of the distance indicator wheel 18 may beconfigured to mesh with each other in frictional engagement such thatthe contact surface of at least the inner cylindrical portion 17 b andthe flange portion 18 c will produce a frictional force or a frictionmaterial (e.g., resin material such as rubber) may be glued to at leastone of the contact surfaces.

Alternatively, at least one of the opposing surfaces of the flangeportion 17 h and flange portion 18 c may be subjected to surfacetreatment so as to increase a friction coefficient between the twosurfaces. As an example, according to the present embodiment, rubber(made of resin material) which is a high-friction material 17 i is gluedto a main-body-side surface of the flange portion 17 h.

As described above, according to the present embodiment, since theengagement between the operation ring 17 and the distance indicatorwheel 18 is maintained by the friction between the two, when theoperation ring 17 is moved to the main-body position (second position),the distance indicator wheel 18 can be turned together.

Regarding the rest of the configuration and operation, the camera system1 according to the third embodiment is similar to the first or secondembodiment. Thus, the camera system 1 according to the third embodimentprovides advantages similar to those of the first or second embodiment.

Fourth Embodiment

A fourth embodiment of the present invention will be described belowwith reference to FIGS. 19 and 20.

The fourth embodiment differs from the first embodiment only in how theoperation ring 17 and the distance indicator wheel 18 are configured tobe engaged with each other. Differences from the first embodiment willonly be described below, wherein components similar to those of thefirst embodiment are denoted by the same reference numerals as thecorresponding components, and description thereof will be omitted asappropriate. A feature of the present embodiment is that the operationring 17 and the distance indicator wheel 18 are engaged with each otherby friction therebetween as in the case of the third embodiment.

FIG. 19 is a partial sectional view of the lens barrel 10 in a state inwhich the operation ring 17 is located on the subject side (firstposition) and the operation ring 17 and the distance indicator wheel 18are not engaged. FIG. 20 is a partial sectional view of the lens barrel10 in a state in which the operation ring 17 is located on the main bodyside (second position) and the operation ring 17 and the distanceindicator wheel 18 are engaged.

In FIGS. 19 and 20, a groove portion 17 m is carved in a circumferentialdirection in the outer circumferential portion of the inner cylindricalportion 17 b of the operation ring 17. A C-ring 17 k substantiallyC-shaped with part of an annular shape cut away is fitted in the grooveportion 17 m. The C-ring 17 k has an inside diameter shaped to fit in abottom face of the groove portion 17 m with a predetermined clearance,and a tapered portion 17 j is provided on an outer circumferentialportion of the C-ring 17 k such that an outer diameter of the C-ring 17k will decrease toward the main body side when the C-ring 17 k is fittedin the groove portion 17 m.

On the other hand, in FIGS. 19 and 20, facing the tapered portion 17 jof the C-ring 17 k, a tapered portion 18 d is formed on the innercircumferential portion of the distance indicator wheel 18 such that theinside diameter of the distance indicator wheel 18 will decrease towardthe main body side.

As shown in FIG. 19, the operation ring 17 is located on the subjectside (first position), and when the operation ring 17 and the distanceindicator wheel 18 are not engaged with each other, the tapered portion17 j of the C-ring 17 k and the tapered portion 18 d of the distanceindicator wheel 18 face each other, being spaced away from each otheralong the optical axis O. Therefore, no frictional force acts betweenthe operation ring 17 and the distance indicator wheel 18. Consequently,the distance indicator wheel 18 does not turn even if the operation ring17 turns.

On the other hand, as shown in FIG. 20, when the operation ring 17 movesfrom the subject side (first position) position to the main body side(second position) position, the C-ring 17 k provided on the operationring 17 moves to the main body side along the optical axis O and thetapered portion 17 j of the C-ring 17 k and the tapered portion 18 d ofthe distance indicator wheel 18 are urged toward the main body side inabutment with each other. This action compresses the C-ring 17 kradially inward in such a way as to reduce the inside diameter of theC-ring 17 k, bringing an inner circumferential surface of the C-ring 17k into contact with the bottom face of the groove portion 17 m.

When the operation ring 17 is located at the second position, an urgingforce which urges the operation ring 17 toward the main body sideprovide a force tending to press the operation ring 17 against thedistance indicator wheel 18, and consequently a frictional force isgenerated between the operation ring 17 and the distance indicator wheel18, allowing both the operation ring 17 and the distance indicator wheel18 to turn.

That is, according to the present embodiment, friction between thetapered portion 17 j and the tapered portion 18 d as well as frictionbetween the inner circumferential surface of the C-ring 17 k and thebottom face of the groove portion 17 m bring the operation ring 17 andthe distance indicator wheel 18 into frictional engagement with eachother, making it possible to reduce an amount of change in the turningposition of the distance indicator wheel 18.

Regarding the rest of the configuration and operation, the camera system1 according to the present embodiment is similar to the first to thirdembodiments. Thus, the camera system 1 according to the presentembodiment provides advantages similar to those of the first to thirdembodiments.

Fifth Embodiment

A fifth embodiment of the present invention will be described below withreference to FIG. 21.

The fifth embodiment differs from the first to fourth embodiments in thefocusing operation mode determination subroutine. Differences from thefirst embodiment will only be described below, wherein componentssimilar to those of the first embodiment are denoted by the samereference numerals as the corresponding components, and descriptionthereof will be omitted as appropriate.

FIG. 21 is a flowchart of the focusing operation mode determinationsubroutine for a camera system according to the fifth embodiment.According to the present embodiment, first, in step S51, the camerasystem 1 determines whether the operation ring 17 exists on the subjectside (first position) or the main body side (second position) based onan output signal from the operation ring front/rear position detectionunit 22. If it is determined in step S51 that the operation ring 17 doesnot exist on the subject side (first position), the camera system 1 goesto step S55, determines that the operation ring 17 exists on the mainbody side (second position) and switches its operation to perform thedistance-specified focusing operation shown in FIG. 14.

On the other hand, if it is determined in step S51 that the operationring 17 exists on the subject side (first position), the camera system 1goes to step S52. In step S52, the camera system 1 determines whether ornot the user has selected the automatic focusing operation mode usingthe focusing mode switching operation portion 5.

If it is determined in step S52 that the automatic focusing operationmode is selected, the camera system 1 goes to step S53 and switches itsoperation to perform automatic focusing operation. On the other hand, ifit is determined in step S52 that the automatic focusing operation modeis not selected, the camera system 1 determines that the operation ring17 exists on the subject side (first position) and that the camerasystem 1 is in manual focusing operation mode, and switches itsoperation to perform the manual focusing operation shown in FIG. 13.

As described above, with the focusing operation mode determinationsubroutine according to the present embodiment, it is determined firstwhether the operation ring 17 is located at the first position or thesecond position. Consequently, if the operation ring 17 is located atthe second position, control is performed such that the focusingoperation mode determination subroutine will end by executing step S55.After the camera system 1 is switched to the operation corresponding toany of steps S53 to S55, when the corresponding subroutine is executedand terminated, the camera system 1 returns to the main sequence of thecamera.

According to the present embodiment, when the user moves the operationring 17 to the second position, the camera system 1 always performsdistance-specified focusing operation. This allows the user to switchquickly to distance-specified focusing operation that uses the distancescale from a state of performing automatic focusing operation.

Except for the focusing operation mode determination subroutinedescribed above, the configuration of the present embodiment is similarto the first embodiment. Thus, the camera system 1 according to thepresent embodiment provides advantages similar to those of the first tofourth embodiments described above.

It should be noted that the present invention is not limited to theembodiments described above. Thus, needless to say, various alterationsand applications are possible without departing from the spirit of theinvention. Furthermore, the embodiments described above includeinventions at various stages, and various inventions can be extractedthrough appropriate combinations of the disclosed components. Forexample, even if some of the components are removed from any of theembodiments described above, the resulting configuration can beextracted as a form of the present invention as long as theconfiguration can solve the problems to be solved by the invention andprovide the advantages described above. Accordingly, the presentinvention is to be limited only by the appended claims and not by anyspecific embodiment thereof.

The present invention is applicable not only to the camera system whichhas the form of a digital camera described in the above embodiments, butalso to electronic devices equipped with an image pickup function, suchas recording devices, portable communications terminals, personalcomputers, game machines, digital media players, television sets, GPSnavigation systems, and watches.

What is claimed is:
 1. A lens barrel comprising: a fixed portion inwhich an optical system including a focusing lens is placed; anoperation member placed so as to be movable to a first position and asecond position along an optical axis of the fixed portion and turnablearound the optical axis at each of the first position and the secondposition; a turning member adapted to turn along with the operationmember when the operation member moves to the second position, and notto operate along with the operation member when the operation membermoves from the second position to the first position; positioning meanswhich positions the operation member at the first position or at thesecond position with respect to the fixed portion, through a pluralityof balls, wherein the positioning means includes a rib portion having asubstantially triangular shape in a cross section along the optical axisand an elastic member which presses the balls against the rib portion,when the operation member is located at the first position, theoperation member is urged in a first direction to be positioned at thefirst position by the plurality of balls being placed in abutment withthe first sloping portion of the rib portion by the elastic member, andwhen the operation member is located at the second position, theoperation member is urged in a second direction opposite to the firstdirection to be positioned at the second position by the plurality ofballs being placed in abutment with the second sloping portion of therib portion by the elastic member.
 2. The lens barrel according to claim1, wherein the first sloping portion forming the rib portion having thesubstantially triangular shape is provided in plurality such that aninside diameter decreases toward a direction of the first position alongthe optical axis, and the second sloping portion formed at the ribportion having the substantially triangular shape is provided inplurality such that an inside diameter increases toward a direction ofthe second position along the optical axis.
 3. The lens barrel accordingto claim 2, wherein the rib portion is formed circumferentially aroundthe entire circumference on an inner side in a diameter direction of theoperation member, the fixing portion includes through-holes in which theballs are placed, the elastic member presses the balls placed in thethrough-holes against the first sloping portion or the second slopingportion formed at the rib portion.
 4. The lens barrel according to claim1, further comprising: first detection means adapted to detect a turningposition of the turning member when the operation member and the turningmember turn in engagement at the second position; second detection meansadapted to detect a turning amount and a rotational direction of theoperation member when the operation member turns by being disengagedfrom the turning member after moving to the first position; and movingmeans placed in the fixed portion and adapted to move the focusing lensalong the optical axis based on a computational value obtained bycomputation using at least an output value from the first or seconddetection means.
 5. The lens barrel according to claim 4, wherein themoving means is controlled so as to move the focusing lens to apredetermined position starting from a current position of the focusinglens by an amount of travel based on the turning amount detected by thefirst detection means when moving the focusing lens along the opticalaxis based on an output from the first detection means, and controlledso as to move the focusing lens to a predetermined correspondingposition using the turning position detected by the second detectionmeans as an absolute position when moving the focusing lens along theoptical axis based on an output from the second detection means.
 6. Thelens barrel according to claim 1, wherein: an index indicator unitindicating aperture stops is provided at a predetermined position on thefixed portion; a distance indicator unit corresponding to the indexindicator unit is provided at a predetermined position on an outercircumferential portion of the turning member; and the distanceindicator unit provided on the turning member is exposed when theturning member moves to the second position, and is hidden by beingcovered with the operation member when the turning member moves from thesecond position to the first position.
 7. The lens barrel according toclaim 1, wherein a convex portion is provided on one of the operationmember and the turning member, and an engaging portion adapted to engagewith the convex portion is provided on the other of the operation memberand the turning member.
 8. The lens barrel according to claim 7, whereinthe engaging portion is a plurality of convex blocks placed at equalintervals on the other of the operation member and the turning member.9. The lens barrel according to claim 1, wherein engagement between theturning member and the operation member is a frictional engagement. 10.The lens barrel according to claim 9, wherein a tapered portion having atapered shape in the cross section along the optical axis is formed onan inner circumferential surface of the turning member, a ring member isplaced on an outer circumferential surface of the operation member, andwhen the operation member moves to the second position, the turningmember and the operation member are integrated due to friction betweenthe ring member placed on the outer circumferential surface of theoperation member and the tapered portion.
 11. A camera comprising a lensbarrel, the lens barrel comprising: a fixed portion in which an opticalsystem including a focusing lens is placed; an operation member placedso as to be movable to a first position and a second position along anoptical axis of the fixed portion and turnable around the optical axisat each of the first position and second position; a turning memberadapted to turn along with the operation member when the operationmember moves to the second position, and not to operate along with theoperation member when the operation member moves from the secondposition to the first position; positioning means which positions theoperation member at the first position or at the second position withrespect to the fixed portion through a plurality of balls, wherein thepositioning means includes a rib portion having a substantiallytriangular shape in a cross section along the optical axis, and anelastic member which presses the balls against the rib portion, when theoperation member is located at the first position, the operation memberis urged in a first direction to be positioned at the first position bythe plurality of balls being placed in abutment with the first slopingportion of the rib portion by the elastic member, and when the operationmember is located at the second position, the operation member is urgedin a second direction opposite to the first direction to be positionedat the second position by the plurality of balls being placed inabutment with the second sloping portion of the rib portion by theelastic member.